Chain plate leak

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tyce

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My chain plates are leaking a little on my Moody31. They are the type that go through the deck with a plate over them, access seems easy enough - release bottle screw on rigging and lift plate so i was wondering what the best stuff to seal with is, would good old silicone sealant suffice or should i go for sika 291.
 
Silicone is fine in your bathroom. Its adhesion and strength are pretty poor, especially in the medium to long term. I never use it on the boat. Whereas Sikaflex 291 keeps its properties for a very long time. My chain plates, stanchion bases, genoa track and many other fittings have been sealed with it, some as long ago as 12-14 years, and still OK.

A tip, though. Toolstation sell a polyurethane sealant called PU 40 that is indistinguishable from Sikaflex 291. It costs less than £5 per tube.
 
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What Vyv says. I do use silicone on my boat for odd small jobs (it's a lot cheaper when the whole tube goes off after using half a millilitre of sealant!). But for anything serious, esp when you're going to use a fair bit in one sitting, then go for a proper marine sealant. Works better, and lasts better.
 
Had the same issues last year on my M31
just lift the chain plates and remove the old sealant, clean and reseal with marine rubber sealant.

problem was solved since then. Do all chain plates since it takes not much time and solve your issues.

grtz
 
While you are doing it, check the chain plate bolts. Although they should be A4 stainless, some boatbuilders use machine screws or studding rather than proper bolts. The snag with this is that a threaded part of the fixing is in the airless, possibly damp and salty hole through the chainplate and bulkhead. Under these conditions crevice corrosion can take place in the threads. It's well worth a few quid to use proper A4 bolts on which the part within the boat structures is smooth, not threaded.
 
tyce said:
My chain plates are leaking a little on my Moody31. They are the type that go through the deck with a plate over them, access seems easy enough - release bottle screw on rigging and lift plate so i was wondering what the best stuff to seal with is, would good old silicone sealant suffice or should i go for sika 291.
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For the reasons ducibella gives make sure you throughly seal the fittings to the deck and where they passes through the deck to eliminate the possibility of water finding its way into any crevice between them. Id take them right out clean them up, inspect them and if sound refit them. You might get a nasty surprise if any have been leaking for long

We nearly lost the rig a few years ago when such a fitting failed due to crevice corrosion. Fortunately a keen eyed crew member spotted a short length of threaded stainless steel and a couple of nuts on the cabin floor!

One other failed as we tried to undo the nuts.
 
Thanks all for the info, marine sealant it is.
I am planning on checking the chain plates in the winter lay up as theres a bit more involved in it in a Moody than some other boats.
 
Rather than wait until the winter, undo the two set screws on each deck plate around the chain plate and as Erwin says rake out the old sealant with a screw driver and stanley knife, then seal back down again. They don't lift up very much but enough to clean out the old sealant. You don't need to touch the bottle screws. Don't forget the baby stay supporting the mast. This was enough to stop the leaks for us. Total time was about a hour for all 5 plates.

The Moody Owners Association have found this stuff:

http://www.marinemastics.com/marine-flex/marine-flex-five-tubes.html

Pete
 
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vyv_cox said:
Silicone is fine in your bathroom. Its adhesion and strength are pretty poor, especially in the medium to long term. I never use it on the boat. Whereas Sikaflex 291 keeps its properties for a very long time. My chain plates, stanchion bases, genoa track and many other fittings have been sealed with it, some as long ago as 12-14 years, and still OK.

A tip, though. Toolstation sell a polyurethane sealant called PU 40 that is indistinguishable from Sikaflex 291. It costs less than £5 per tube.
Click to expand...

Just used PU40 on HB when fitting new strake.
It takes 2-3 days longer to cure than sika, and does not cure as stiff as sika.
Because of this I dident use it when I rebedded the stancion basses, I used Sikaflex, although PU40 is good, why jepordise a good job for the sake of £8 odds.
C_W
 
I think you should use 292i because chain plates are going to move in relation to the deck and 292i is very flexible .
"292i for structural joints in marine constructions which will be subjected to high dynamic stresses"
Well that's what the Sika rep told me.
 
auditdata said:
I think you should use 292i because chain plates are going to move in relation to the deck and 292i is very flexible .
"292i for structural joints in marine constructions which will be subjected to high dynamic stresses"
Well that's what the Sika rep told me.
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292 ( 292i) is primarily a structural bonding adhesive.

291 or 291i is an adhesive sealant. That's the one to use from the Sika Marine range. But the PU40 That Vyv suggests should do equally well
 
Clyde_Wanderer said:
Just used PU40 on HB when fitting new strake.
It takes 2-3 days longer to cure than sika, and does not cure as stiff as sika.
Because of this I dident use it when I rebedded the stancion basses, I used Sikaflex, although PU40 is good, why jepordise a good job for the sake of £8 odds.
C_W
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I have not noticed that. I have used two tubes now, one in winter Milford Haven, the other in Greece. Both seemed to behave, feel and make just as much mess as Sikaflex. Maybe yours was old stock, faulty?
 
It wasnt that i didnt want to pay for the sika i was thinking it would be a nightmare to dig it out in a few years when it needs doing again.
Thanks all for excellent advice.
 
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